Macrophages possess cytostatic and cytotoxic activities against neoplastic cells. During growth of syngeneic tumors in rats or mice, however, there occurs a progressive inhibition of macrophage accumulation in induced peritoneal exudates. This effect could compromise cellular immunity permitting tumors to survive despite manifest immune responses. The proposed work seeks to ascertain the factors involved in this abnormal monocyte inflammatory reaction. The work will determine also if the phenomenon limits the inflammatory response in tissues as well as in the peritoneal cavity. Further, we will determine the relationship, if any, between inflammation measured at sites distant to the tumor and the accumulation of macrophages within the tumor.